Home > Articles

An Overview of Cisco IOS Versions and Naming

Version and naming structure used by Cisco for their IOS images is often confusing. Although the naming used for some of the newer devices is changing to a simpler structure, it will be a while before all the different versions are consolidated. This article covers these different releases and aims to give a single location where network engineers can look to figure out what the different releases mean
Like this article? We recommend

One thing that is often confusing to any network engineer (regardless of level) is the version and naming structure used by Cisco for their IOS images. Although the naming used for some of the newer devices is changing to a simpler structure, it will be a while before all the different versions are consolidated. This article covers these different releases and aims to give a single location where network engineers can look to figure out what the different releases mean. Although this is not an exhaustive list of every Cisco version, it does cover the most commonly used versions.

IOS Releases

One term that is often used is the IOS release type. With versions of IOS earlier than 15, a specific image could be considered one of the following four different release types:

Early Deployment (ED): These releases provide both new features and new platform support in addition to bug fixes.

Limited Deployment (LD): These releases do not include any new features or platform support but do include bug fixes. LD releases are between an ED release and a GD release.

General Deployment (GD): These releases can be used anywhere in a customer network with the same feature and functionality requirements. These tend to be stable on almost all platforms.

Maintenance Deployment (MD): These releases are used to provide additional support for bug fixes and ongoing software maintenance.

With IOS 15 and later, both the LD and GD deployments will be retired. New releases will be considered either ED or MD. The IOS train paths have also been consolidated. With earlier versions of IOS, the different ED (T trains; for instance, 12.4T) and MD (not T trains; for instance, 12.4) has different code bases. With IOS 15 and later, the code bases will be consolidated. MD releases (called M releases, or extended release) will be released and have a 44-month support window, whereas ED (T releases, or standard release) will have a 18-month support window.

IOS Versions

A number of different versions exist within each release of IOS. This article takes a look at a few of these and how what they are used for.

12

With IOS Version 12, many different sub-versions of IOS exist, including specialized support for specific platforms; the next few sections cover a couple of the most common.

IOS Version 12 has a few different ways to notate version, including those shown in Figure 1.

Figure 1 IOS Version 12 Version Notation

12

The 12 base versions are also referred to as the mainline release of a version. These releases tend to be the most stable and include support for most of the available platforms. Other more specialized versions of IOS are rolled into the mainline as an update when they have been sufficiently tested. (They go through the release process shown in the previous section.)

12T

The T train is used to add the newest features and platforms. After the software has been tested thoroughly, it is rolled into the mainline release.

12S, 12SB, 12SR

Many different IOS versions provide support for specific platforms. The ones shown in the section name are an incomplete list but do show some of the common examples. The 12S, 12SB, and 12SR versions tend to provide support for Cisco’s 7200, 7300, 7400, 7500, and 10000 platforms.

15

The way that different versions are referenced with IOS Version 15 is similar to that of IOS Version 12.

IOS Version 15 has a notation that is similar to IOS Version 12 and is shown in Figure 2.

Figure 2 IOS Version 15 Version Notation

15M

As with IOS version 12, IOS Version 15M provides a mainline release and is also referred to as a maintenance release.

15T

As with IOS version 12T, version 15T is focused on new features and platforms and is supported for a shorter amount of time than the maintenance releases. After 15T releases have been tested thoroughly, they are wrapped into the next 15M release.

15X, 15S, 15SY, 15SG, 15SE

As with IOS Version 12, IOS Version 15 is going to have a number of different versions that are specific to new equipment that needs to support new features (specific to the platform). For IOS Version15, some of those currently available are Version 15X (special or early deployment), 15S (7600), 15Y (Sup-2T-10GE – Catalyst 6500), 15SG (Sup-CS-S2T – Catalyst 6500), and 15SE (2960, 3560, 3650, and 3750 platforms).

IOS Package Naming

The way that Cisco has named their IOS packages has changed over time. With IOS Version 12.3 though 15, this has remained relatively constant. Figure 3 shows the eight different packages that are available.

Figure 3 IOS Software Packaging (Routers and Switches)

Of course, this can get confusing. In an effort to make the software licensing process simpler and provide operational savings, the way that packages are created has changed with the new Integrated Service Routers (ISR) Generation 2. With these devices, a universal image is shipped on each one. The functionality provided by the image is dictated by the features enabled with a license key.

Figure 4 shows the four different packages that are available.

Figure 4 IOS Software Packaging (ISR G2 Routers)

Each of these are then able to be added together to obtain the features required in each situation (for example, UC + Security or Data + Security).

Summary

Well, leave it up to development to have a structure that makes sense to only a small number of people. This certainly seems to have happened with the various iterations of IOS. This article should enable current and new network engineers to break down what every image provides so that future IOS version selection becomes easier. Let’s hope that going forward the model being used for the newer ISR G2 will be used. At the very least, this will make the selection of the most appropriate IOS image feature package possible without considerable time spend with Cisco presales.

Pearson IT Certification Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Pearson IT Certification and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Pearson IT Certification products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by Adobe Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.pearsonitcertification.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020